Test: Double Fertilisation & Post Fertilisation

• In the case of double fertilization, which occurs in angiosperms, the primary nucleus fused with one of the nuclei of male gamete and produces zygote and secondary nucleus fuses with another nucleus of the male gametes and forms endosperm.
• Endosperm provides nourishment for the developing embryo. The other male gamete which enters the embryo sac fuses with the haploid egg and forms the embryo.

Thus, the correct answer is option D.

Synergids or synergid cells are haploid accessory cells at the micropylar pole of the angiosperm embryo sac; glandular-like cells involved in pollen tube attraction and reception.

► Megapore is a haploid structure which divides and gives rise to embryo sac which is also called as female gametophyte.

► Eight-nucleate embryo sacs may be:

• Monosporic (Example: Polygonum)
• Bisporic (Example: Allium) 
• Tetrasporic (Example: Adoxa).

• Endosperm is formed during double fertilization.
• It is triploid because it is formed when one of the two sperm that is haploid enters inside the embryo sac & fuses with two polar nuclei (each polar nuclei is haploid).
• So the endosperm formed is triploid.

In the sixteen-cell stage of the embryo in dicots, the eight protodermal cells divide further by anticlinal division to form the embryonic surface layer, while the inner eight cells divide in different planes to form the ground meristem and procambium.

Aleurone is a protein found in protein granules of maturing seeds and tubers. It also describes one of the two major cell types of the endosperm, the aleurone layer. It is the outermost layer of the endosperm.

Structure of Maize Seed:

• The pollen grains germinate on the stigma and the resulting pollen tubes grow through the tissues of stigma and style and reach the ovule.
• The pollen tubes enter the embryo-sac where two male gametes are discharged. One of the male gametes fuses with the egg cell (syngamy) and forms a diploid zygote. The other male gamete fuses with the diploid secondary nucleus to four primary endosperm nucleus (PEN), which is triploid in nature.
• Since, two types of fusion. syngamy and triple fusion takes place in the embryo sac, the process is known as double fertilisation. 
  

• In pea, endosperm is consumed by developing embryo in the seed.
• The endosperm is completely absorbed by the growing embryo and the food reserve gets stored in the cotyledons.
• Such seeds are called non-endospermic or exalbuminous.

Parthenocarpy (parthenos-virgin, karpos-fruit) is the formation of seed less fruits without fertilization. The fruits developed from unfertilized ovary are called parthenocarpic fruits.

Other options are incorrect because:

• In asexual reproduction, a single individual (parent) is capable of producing offspring.
• For apomixis and sexual reproduction. 

• The fusion of one male gamete with the egg cell is called Syngamy or true fertilization while the fusion of second male gamete with two polar nuclei is called triple fusion.
• Syngamy along with the triple fusion is called double fertilization. Double fertilization is a characteristic feature of flowering plants or angiosperms.